Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
When the speed control actuator carries out the self-test, it checks for continuity to ground through circuit 199 (LB/YE). This is accomplished by sending a voltage reference signal to the clutch pedal position (CPP) switch (manual transaxle) or the transmission range (TR) sensor (automatic transaxle).
When the clutch is applied, the signal is routed through circuit 359 (GY/RD) to the powertrain control module (PCM). The PCM provides an internal ground.
When the automatic transaxle is in NEUTRAL, the signal is routed through circuit 57 (BK) to ground.